Dr. Smasher

What are the stock running temp ranges for an auto?

no_6_oh_no

140 to 240 degrees is the operating range. 190 is about the norm under load locked up in warm weather. That is measured at the cooler output line.

Cooler weather the running temps will vary down. In warm weather and stop-n-go driving with the TC unlocked they go up. Usually, if you see 160-220 year round in all driving conditions its normal.

Pull Dog

My 05 has the temp sensor in the output line and are identical with these readings. With the TC unlocked the temp will spike up quite rapidly but I have never seen over 220 in stop and go slow traffic. In cool damp weather I see about 160 on the Interstate while towing light loads

.boB

I use a Bully Dog Outlook moniter for gauges. I doubt it's quite as accurate as a good set of Autometer gauges, but they should be close enough. It reads the same data the ECU does.

The stock temp sensor is in the pan. Not the hottest part of the trans.

I don't think I've ever seen the trans temp above 140* or so. I tow lightly, probably no more than 5K#. But I don't think twice about setting the cruise control at 75 run it up and down the rocky mountains.

Why so cool? A pan temp of 120* = ??* at the cooler outlet?

Dr. Smasher

What does it matter where the temps are taken? As long as they are safe for that location. If a pan temp should not go higher than lets just say 220 than it is what it is.

I'm just saying because I have the Mag-Hytec double deep pan and it already has a bung for the temp sending unit. Why would it be necessary to put one in the lines?

Thanks all for the replies.

no_6_oh_no

Oh, now you opened THAT can of worms.

The why depends a lot on how you use your truck and drive it. Lets take a quick look at fluid flow in an automatic transmission for that answer.

The bulk of the fluid used in an automatice transmission is used in the TC in fluid coupling. The rest is use dto aplly clutches and keep the sump full. Coincidently, becuase of the fluid coupling about 90% of the heat generated in the transmission is generated in the TC due to fluid shear. The rest of the heat is generated in the drive train by the pressure on bushings, thrust washers pinions, etc.

Pan fluid is a mixture of cooled fluid that has been run thru the drive train for cooling and lube, sump fluid, and fluid dumped back by the TC. When you read pan temps its not treally indicative of how hard the trans is being worked because of the mixing. If you drive proactive, your adjusting driving before fluid temp is a problem as opposed to reactive where your dealing with the problem when it is a big problem. This is where the probe placement becomes effective.

Fluid flow in the transmission with the TC not locked runs about 20 psi of pressure thru the cooler lines with the rest of the fluid dumping back to the sump to be used again. Its a rather small percentage that is actually circulated in fluid coupling to keep the TC happy. All the fluid coming back fromthe TC in fluid coupling is hot. How hot is dependent on just how hard your working the trans. You now have cooled fluid mixing with hot TC fluid in the sump and that is what you are reading. Your temps don't rise as fast and you never see what the max temp was out of the TC because it is a mixed media being read.

When the TC is locked its a different story. There is no fluid being used to transfer power as the clutch is locked so all the fluid is used for apply pressure. The lfuid return back from the TC at that point is mostly routed thru the cooler, its line pressure applied to an orfice in the cooler output circuit. Some fluid is still run back to the sump because it won't all fit thru the cooler but a larger portion is circulated and cooled.

So, temp probe in the pan reads a mix of fluid temps all the time, locked or unlocked. You can't tell how hard oyur working the trans. You could have fluid in excess of 300 degrees out of the TC mixing with 130 degree fluid from th ecooler and your temps never exceed 200-210 degrees which is normal, but, you won't know your working the TC too hard until those pan temps take a long time to heat up. You can only react when the temp gets to high or the trans temp light comes on.

Now, probe in the cooler output line. You ALWAYS see the hottest temps in the trans immediately because the fluid in the cooler output line is directly out of the TC. In fludi coupling you can wath it rise as you heat the fluid and work the trans harder. You can gear down, slow down, lock the TC, etc, if that temp starts getting out of hand. In lcokup you will still se the hottest temps becuse the fluid is compressed and used to apply the TC clutch and thta is still the hottest point in the trans, but, it will be a lot cooler due to no fluid coupling. Normally that temp is about 20 degrees more than pan temp in lockup.

You see its about being proactive or reactive and wanting to know the conditions as soon as possible. That won't happen in the pan, but, it is immediately seen in the cooler output line.

Dr. Smasher

OK so the where is the cooler output line and what coupling should I use?

no_6_oh_no

Front line on the trans is the output line. You can either get a fitting that will fit the hard line, DieselManor has them, or get a fitting the will fit in the rubber isolator portion of the line.